As one of research themes of ITS (Intelligent Transport Systems) for improving the transportation efficiency and comfortableness of road traffics by applying IT technologies, there is an LKS (Lane Keep Support) system. This is a system which recognizes a lane on a road by a sensor, and controls a steering, an accelerator, a brake, and the like so that an automobile can always run on the center of a lane based thereupon.
The important thing for achieving the LKS system is a lane recognition technique. Particularly, actively studied is a technique with which an image input device such as a camera is placed in the front or rear side of a running vehicle, and the image input device processes images picked up while running on a road to recognize a lane line drawn on the road in a high-luminance color such as white or yellow.
FIG. 18 is a conceptual illustration showing an example of the structure of a widely-used lane recognition device 1800 depicted in Patent Document 1. The widely-used lane recognition device 1800 is configured with an image input device 1810, a bird's-eye image creation module 1820, a luminance profile creation module 1830, and a lane line detection module 1840.
FIG. 19 is a conceptual illustration showing actions of the lane recognition device 1800 shown in FIG. 18. FIG. 19A is an image of a road while running thereon picked up by the image input device 1810. This is called an original image 1910. The bird's-eye image creation module 1820 to which the original image 1910 is inputted creates a bird's-eye image shown in FIG. 19B from the original image 1910.
The luminance profile creation module 1830 detects integral luminance shown in FIG. 19C by each coordinate in the road-width direction by integrating luminance of coordinates in the direction orthogonal to the road-width direction of the road surface shown in the bird's-eye image 1920. At last, the lane line detection module 1840 obtains a position which corresponds to a coordinate of the road-width direction showing higher integral luminance than the integral luminance distribution to detect a lane line 1930.
Other than Patent Document 1, there are following documents regarding recognition of lanes. Patent Document 2 discloses an example of a technique which detects a lane from an original image. Patent Document 3 discloses an example of a technique which creates a synthesized bird's-eye image from bird's-eye images based on the shift amount on a plane. Patent Document 4 discloses an example of a technique which detects a position and a type of a lane from an original image. Patent Document 5 discloses an example of a technique which judges whether a lane detected from an original image is a solid line or a broken line.
Patent Document 6 discloses an example of a technique which improves lane detection accuracy by using a plurality of images of different points of time. Patent Document 7 discloses an example of a technique which improves the lane detection accuracy based on fluctuations in a luminance total value. Patent Document 8 discloses an example of a technique which improves the lane detection accuracy by judging the road surface state by providing various kinds of sensors to a vehicle.
Patent Document 9 discloses a technique which acquires a bird's-eye image of the surroundings of a vehicle by connecting a plurality of images of different points of time. Patent Document 10 discloses an example of a technique which improves the image quality when acquiring a bird's-eye image from an original image. Patent Document 11 discloses an example of a technique which improves the lane detection accuracy by separately recognizing a lane from a short distance and a long distance.
Patent Document 1: Japanese Unexamined Patent Publication 2004-145852
Patent Document 2: Japanese Unexamined Patent Publication 2000-242769
Patent Document 3: Japanese Unexamined Patent Publication 2002-120675
Patent Document 4: Japanese Unexamined Patent Publication 2002-175534
Patent Document 5: Japanese Unexamined Patent Publication 2003-067755
Patent Document 6: Japanese Unexamined Patent Publication 2003-346163
Patent Document 7: Japanese Unexamined Patent Publication 2004-246641
Patent Document 8: Japanese Unexamined Patent Publication 2005-276041
Patent Document 9: Japanese Unexamined Patent Publication 2007-096497
Patent Document 10: Japanese Unexamined Patent Publication 2007-249392
Patent Document 11: Japanese Unexamined Patent Publication Hei 09-167239